1. Field of the Invention
The present invention relates to a display device, and more particularly to a display device in which an optical switching element is provided in each of a plurality of pixels.
2. Description of the Background Art
In recent years, various types of display devices have been developed in the art, such as liquid crystal display devices and organic EL (electroluminescence) display devices. Particularly, active matrix type display devices, in which a switching element is provided in each of a plurality of pixels, have been actively developed in the art.
A thin film transistor (TFT) is widely used as a switching element in active matrix type display devices. A plurality of TFTs are formed in a matrix pattern on a TFT substrate. The TFT substrate includes scanning signal lines for applying scanning signals to the TFTs, and data signal lines for applying data signals thereto.
The scanning signal lines and the data signal lines extend in the respective directions that cross each other (typically perpendicular to each other). Therefore, at each intersection therebetween, a scanning signal line and a data signal line, which are made of a conductive material such as a metal, oppose each other via an insulative film therebetween, thus forming a capacitor. Such a capacitor formed at each intersection causes a signal delay, thereby adversely influencing the display.
In order to prevent a signal delay by the formation of such an unnecessary capacitor, it has been proposed in the art to employ, as a switching element, an optical switching element that is turned ON by being irradiated with light.
For example, Japanese Laid-Open Patent Publication No. 1-173016 and Japanese Laid-Open Patent Publication No. 4-367826 each disclose a liquid crystal display device including an optical switching element provided in each pixel, and a scanning signal light emitting element for emitting light as a scanning signal to the optical switching element.
In the liquid crystal display devices disclosed in these publications, a scanning signal light emitting element, which is a linear light emitting element or a linear light guide element having a light emitting element at an end thereof, functions as a scanning signal line in a conventional TFT substrate. Therefore, the unnecessary capacitor as described above is not formed, thereby preventing a signal delay.
However, a display device in which an optical switching element is provided in each pixel as those liquid crystal display devices described above has a problem, so called xe2x80x9ccrosstalk phenomenonxe2x80x9d. A crosstalk phenomenon is caused when light emitted from a scanning signal light emitting element that is associated with an optical switching element is incident on a different, unintended optical switching element.
Japanese Laid-Open Patent Publication No. 10-288965 discloses an organic EL display device including a pin hole mask, which transmits only a portion of light emitted from scanning signal light emitting elements that travels straight toward optical switching elements, in order to suppress the occurrence of a crosstalk phenomenon.
However, the present inventor has found that the use of a pin hole mask may not always prevent light from being incident on an unintended optical switching element depending on the arrangement of the optical switching elements and the scanning signal light emitting elements, in which case the occurrence of a crosstalk phenomenon is not suppressed sufficiently.
Moreover, the present inventor has also found that in a display device including a backside light source, e.g., a liquid crystal display device including a backlight, a crosstalk phenomenon may be caused also by light from the backside light source.
The present invention has been made to solve the problems as set forth above, and has an object to provide a display device capable of displaying an image with a high quality while suppressing the occurrence of a signal delay and a crosstalk phenomenon.
A first display device of the present invention includes: a plurality of pixel electrodes defining a plurality of pixels that are arranged in a matrix pattern; optical switching elements electrically connected to the plurality of pixel electrodes, respectively; and scanning signal light emitting elements for emitting dotted light, as scanning signals, to the optical switching elements, wherein a distance between the optical switching element and the scanning signal light emitting element is less than a pixel pitch at which the plurality of pixels are arranged. Thus, the object set forth above is realized.
A second display device of the present invention includes: a plurality of pixel electrodes defining a plurality of pixels that are arranged in a matrix pattern; optical switching elements electrically connected to the plurality of pixel electrodes, respectively; scanning signal light emitting elements for emitting dotted light, as scanning signals, to the optical switching elements; and a louver provided between the optical switching element and the scanning signal light emitting element. Thus, the object set forth above is realized.
A third display device of the present invention includes: a plurality of pixel electrodes defining a plurality of pixels that are arranged in a matrix pattern; optical switching elements electrically connected to the plurality of pixel electrodes, respectively; scanning signal light emitting elements for emitting dotted light, as scanning signals, to the optical switching elements; and a focusing element provided between the optical switching element and the scanning signal light emitting element for focusing light emitted from the scanning signal light emitting element on a predetermined area. Thus, the object set forth above is realized.
The focusing element may be a lens.
The display device may further include: a backlight provided on a side away from the optical switching element with respect to the scanning signal light emitting element; and a light blocking layer provided on a side of the scanning signal light emitting element that is closer to the backlight.
It is preferred that light emitted from the scanning signal light emitting element is modulated into a predetermined polarized state, and substantially only light that is in the predetermined polarized state is incident on the optical switching element.
A fourth display device of the present invention includes: a plurality of pixel electrodes defining a plurality of pixels that are arranged in a matrix pattern; optical switching elements electrically connected to the plurality of pixel electrodes, respectively; and scanning signal light emitting elements for emitting dotted light, as scanning signals, to the optical switching elements, wherein light emitted from the scanning signal light emitting element is modulated into a predetermined polarized state, and substantially only light that is in the predetermined polarized state is incident on the optical switching element. Thus, the object set forth above is realized.
The display device may further include: a first polarizing element provided between the optical switching element and the scanning signal light emitting element for modulating light emitted from the scanning signal light emitting element into the predetermined polarized state; and a second polarizing element provided between the first polarizing element and the optical switching element and arranged so as to selectively transmit light that is in the predetermined polarized state.
The display device may further include: at least one counter electrode opposing the plurality of pixel electrodes; and a liquid crystal layer provided between the plurality of pixel electrodes and the at least one counter electrode.
The display device may further include: at least one counter electrode opposing the plurality of pixel electrodes; and an organic electroluminescence material layer provided between the plurality of pixel electrodes and the at least one counter electrode.
It is preferred that the display device further includes a light blocking layer provided on a viewer side of the optical switching element.
It is preferred that the scanning signal light emitting element is formed in a dot-like shape.
A fifth display device of the present invention includes: a plurality of pixel electrodes defining a plurality of pixels that are arranged in a matrix pattern; optical switching elements electrically connected to the plurality of pixel electrodes, respectively; and scanning signal light emitting elements, respectively associated with the optical switching elements, for emitting light, as scanning signals, to the optical switching elements, wherein the scanning signal light emitting element is formed in a dot-like shape, and substantially only light that is emitted from one scanning signal light emitting element that is associated with one optical switching element is incident on the optical switching element.
A distance between one optical switching element and one scanning signal light emitting element that is associated with the optical switching element may be less than a pixel pitch at which the plurality of pixels are arranged.
The display device may further include a louver between at least one optical switching element and at least one scanning signal light emitting element that is associated with the at least one optical switching element.
The display device may further include a focusing element between at least one optical switching element and at least one scanning signal light emitting element that is associated with the at least one optical switching element for focusing light emitted from the at least one scanning signal light emitting element on a predetermined area.
The focusing element may be a lens.
The display device may further include: a backlight provided on a side away from the optical switching element with respect to the scanning signal light emitting element; and a light blocking layer provided on a side of the scanning signal light emitting element that is closer to the backlight.
It is preferred that light emitted from each scanning signal light emitting element is modulated into a predetermined polarized state, and substantially only light that is in the predetermined polarized state is incident on one optical switching element that is associated with the scanning signal light emitting element.
The display device may further include: a first polarizing element provided between at least one optical switching element and at least one scanning signal light emitting element that is associated with the at least one optical switching element for modulating light emitted from the at least one scanning signal light emitting element into the predetermined polarized state; and a second polarizing element provided between the first polarizing element and the at least one optical switching element and arranged so as to selectively transmit light that is in the predetermined polarized state.
The display device may further include: at least one counter electrode opposing the plurality of pixel electrodes; and a liquid crystal layer provided between the plurality of pixel electrodes and the at least one counter electrode.
The display device may further include: at least one counter electrode opposing the plurality of pixel electrodes; and an organic electroluminescence material layer provided between the plurality of pixel electrodes and the at least one counter electrode.
It is preferred that the display device further includes a light blocking layer provided on a viewer side of the optical switching element.
Functions of the present invention will now be described.
In the first display device of the present invention, the distance between the optical switching element and the scanning signal light emitting element is less than the pixel pitch at which the plurality of pixels are arranged, thereby preventing light emitted from a scanning signal light emitting element in one pixel from being incident on an unintended optical switching element in an adjacent pixel. Thus, the occurrence of a crosstalk phenomenon is suppressed, and an image is displayed with a high quality.
The second display device of the present invention includes a louver provided between the optical switching element and the scanning signal light emitting element, whereby light that is emitted obliquely from the scanning signal light emitting element is blocked by the louver. Therefore, light that is emitted obliquely from a scanning signal light emitting element in one pixel is prevented from being incident on an unintended optical switching element in an adjacent pixel. Thus, the occurrence of a crosstalk phenomenon is suppressed, and an image is displayed with a high quality.
The third display device of the present invention includes a focusing element provided between the optical switching element and the scanning signal light emitting element for focusing light emitted from the scanning signal light emitting element on a predetermined area. Thus, light emitted from the scanning signal light emitting element is focused on the predetermined area. Therefore, light emitted from a scanning signal light emitting element in one pixel is prevented from being incident on an unintended optical switching element in an adjacent pixel. Thus, the occurrence of a crosstalk phenomenon is suppressed, and an image is displayed with a high quality.
In the fourth display device of the present invention, light emitted from the scanning signal light emitting element is modulated into a predetermined polarized state, and substantially only light that is in the predetermined polarized state is incident on the optical switching element. Therefore, light that is not in the predetermined polarized state is prevented from being incident on the optical switching element. Thus, the occurrence of a crosstalk phenomenon due to light that is not from the scanning signal light emitting element (e.g., light from a backlight in a liquid crystal display device) is suppressed, and an image is displayed with a high quality.
In the fifth display device of the present invention, the scanning signal light emitting element is formed in a dot-like shape, and substantially only light that is emitted from a scanning signal light emitting element that is associated with an optical switching element is incident on the optical switching element. Therefore, the power supplied to the scanning signal light emitting element is efficiently used as scanning signal light, thereby reducing the power consumption. Moreover, light emitted from unintended scanning signal light emitting elements (light emitting elements other than the scanning signal light emitting element that is associated with the optical switching element) will not be incident on the optical switching element, thereby suppressing the occurrence of a crosstalk phenomenon.
The present invention provides a display device capable of displaying an image with a high quality while suppressing the occurrence of a signal delay and a crosstalk phenomenon. The present invention can suitably be used with a liquid crystal display device or an organic EL display device.